The present invention relates to polysiloxanes linked by ether linkages to fluorescent organic moieties. More particularly it relates to such polysiloxane compounds that are fluorescent.
Fluorescent polymers have been of interest for many years. See generally N. Barishnikov et al., Fluorescent Polymers, Horwood, London, UK (1994). Such fluorescent materials are of research interest, and are also of interest in connection with commercial applications (e.g. paints used on highway signage).
Such materials are now receiving even more attention because some fluorescent polymers are also electroluminescent, and so may be useful in polymeric light emitting diodes for advanced display technology. See generally J. Burroughes et al., 347 Nature 359 (1990); M. Bernius et al., 12 Advanced Materials 1737 (2000); S. Jenekhe et al., 265 Science 765 (1994); J. Oshita et al., 18 Organometallics 1453 (1999); S. Yamaguchi et al., J. Chem. Soc. 3963 (1998); B. Tang et al., 11 J. Mater. Chem. 2974 (2001); H. Sohn et al., 121 J. Am. Chem. Soc. 2325 (1999) and S. Yamaguchi et al., 39 Agnew. Chem., Inc. Ed., 1695 (2000).
In U.S. Pat. No. 6,337,383 our laboratory reported a number of techniques for synthesizing polysiloxane polymers, particularly those having multiple oligooxyethylene side chains per silicon. These materials were highly conductive, and thus of interest in connection with lithium batteries. Fluorescence or electroluminescence were not noted in connection with these compounds.
There have been some reports of fluorescent polysiloxanes. The fluorescence of poly(phenylmethylsiloxane) was studied in F. Dias et al., 33 Macromolecules 4772 (2000); the emission spectra of certain cyclic phenylsiloxanes have been investigated as described in M. Backet et al., 729 ACS Symposium Series 115 (2000); and polysiloxanes with pendant carbazolyl groups were observed to show fluorescence as described in M. Hennecke et al., 189 Makromol. Chem. 2601 (1988) and L. Guizhi 15 Gaofenzi Cailiao Kexue Yu Goncheng 105 (1999).
However, the fluorescence of many of such compounds was weak. In other cases, the wavelengths generated were not optimal for certain purposes. In still other cases the light wavelength needed to cause the fluorescence was not convenient for certain commercial purposes, and/or the material was expensive to create and/or had other less than optimal properties.
For example, certain fluorescent compounds have been grafted to polysiloxanes via alkene linkage reactions, resulting in compounds with electroluminescent properties. See generally J. Bisberg et al., 28 Macromolecules 386 (1995) and K. Belfield et al., 31 Macromolecules 2918 (1998). While these materials have certain advantages, they are relatively difficult to synthesize, and in any event have certain wavelength limitations.
Also, in B. Chauhan et al., 20 Organometallics 2729 (2001), there was a report of grafting non-fluorescent aryl compounds to polysiloxanes using a rhodium catalyzed reaction of an aryl alcohol with poly(methylhydrosiloxane). The resulting compounds were of charge-transporting interest, but not reported as being fluorescent.
There is a continuing desire to develop other fluorescent polymers, particularly those that have well defined and intense light properties, where the material is relatively easy to produce, and where the material is in a form rendering it suitable for incorporation into commercial products.